The present invention relates to shift-actuating members, more specifically to actuators that are driven by electric motors and are used for the control of a gear-shifting mechanism of an automatic transmission system in a motor vehicle.
Electrically powered actuators used for the control of gear-shifting mechanisms of automatic transmission systems usually incorporate a worm gear mechanism in order to achieve a high reduction ratio, i.e., to change the high-rpm and relatively low-torque output of the electric motor into a relatively high torque at a low rpm-rate as required for actuating a gear-shifting mechanism. The foregoing concept is disclosed for example in GB 2325036, GB 2313885, and GB 2309761, which are hereby explicitly referenced and whose content will be expressly cited in the disclosure of the present invention. The reduction ratios of these kinds of actuating mechanisms are usually of the order of 40:1 to 60:1.
The worm gear mechanisms used heretofore have the disadvantage that they are relatively large and present serious spatial difficulties in view of the installation constraints that are encountered in automatic transmission systems for motor vehicles.
Further in this regard, special difficulties occur when electrically powered actuators are used with shift cylinders, as disclosed for example in GB 2308874 and GB 2311829, which are hereby explicitly referenced and whose content will be expressly cited in the disclosure of the present invention.
Transmissions of the aforementioned kind are further disclosed in EP 0654624. The shift mechanism of the transmissions in EP 0654624 are driven by an electric motor that is arranged outside of the transmission and uses gear stages to move the shift cylinder for actuating a gear change. Even more space is required if two or more so-called shift cylinders are used for example to also actuate clutches that are associated with transmissions. The actuation by means of a shift cylinder is advantageous, e.g., in the case of dual-clutch transmissions or power-shift transmissions with power-shift clutches.